//bloquear boton derecho
document.oncontextmenu = function(){return false}
//bloquear teclas backspce
if (typeof window.event != 'undefined') // para internet explorer
    document.onkeydown = function(){
        var t=event.srcElement.type;
        var kc=event.keyCode;
        return ((kc != 8 && kc != 13) || ( t == 'text' &&  kc != 13 )||(t == 'textarea') ||(t=='password')|| ( t == 'submit' &&  kc == 13))
    }
else{
    document.onkeypress = function(e){  // FireFox/Others
        var t=e.target.type;
        var kc=e.keyCode;
        if ((kc != 8 && kc != 13) || ( t == 'text' &&  kc != 13 )||(t == 'textarea')||(t=='password') || ( t == 'submit' &&  kc == 13))
            return true
        else {
            return false
        }
    }
}